▪ Abstract Observations of redshifted Lyman α (Lyα) forest absorption in the spectra of
quasistellar objects (QSOs) provide a highly sensitive probe of the distribution of gaseous …

Intergalactic space is filled with a pervasive medium of ionized gas, the intergalactic medium
(IGM). A residual neutral fraction is detected in the spectra of quasistellar objects at both low …

We present improved synthesis models of the evolving spectrum of the UV/X-ray diffuse
background, updating and extending our previous results. Five new main components are …

The rapidly expanding field of galaxy formation lies at the interface between astronomy,
particle physics, and cosmology. Covering diverse topics from these disciplines, all of which …

Recent observations indicate that dark matter halos have flat central density profiles.
Cosmological simulations with nonbaryonic dark matter, however, predict self-similar halos …

We present a detailed calculation of the propagation of AGN-like ionizing radiation through
the intergalactic space. We model the ionization state of absorbing clouds, and show that the …

The ionizing continuum from active galactic nuclei is fundamental for interpreting their broad
emission lines and understanding their impact on the surrounding gas. Furthermore, it …

The history of the transition from a neutral intergalactic medium (IGM) to one that is almost
fully ionized can reveal the character of cosmological ionizing sources. We study the …

We use a sample of 332 Hubble Space Telescope spectra of 184 quasi-stellar objects
(QSOs) with z> 0.33 to study the typical ultraviolet spectral properties of QSOs, with …

Cosmological simulations with gas provide a detailed description of the intergalactic
medium, which makes possible predictions of neutral hydrogen absorption in the spectra of …